The first complete plastid genome of Burmannia disticha L. from the mycoheterotrophic monocot family Burmanniaceae

Burmanniaceae is one major group within the monocot order Dioscoreales that has not had its plastome sequenced.Members of Burmanniaceae are mostly achlorophyllous,although the genus Burmannia also includes autotrophs.Here,we report sequencing and analysis of the first Burmanniaceae plastid genome from Burmannia disticha L..This plastome is 157,480 bp and was assembled as a circular sequence with the typical quadripartite structure of plant plastid genomes.This plastome has a regular number of potentially functional genes with a total of 111,including 78 protein coding genes,4 ribosomal RNA(rRNA) genes,and 29 tRNA genes.The ratio of the total length of genic:intergenic DNA is 1.58:1,and the mean length of intergenic regions is 398 bp,the longest being 1918 bp.The overall GC content of the B.disticha plastome is 34.90%,and the IR regions in B.disticha are more GC rich(39.50%) than the LSC(32.30%) and SSC(28.80%) regions.Phylogenetic analysis of protein-coding sequences from plastomes of related species in the order Dioscoreales support a clade comprising Burmanniaceae and Dioscoreaceae.This phylogenetic placement is congruent with previous findings based on nuclear and mitochondrial evidence.

Impact of amplified spontaneous emission noise on the SRS threshold of high-power fiber amplifiers

Impact of amplified spontaneous emission(ASE)noise on the stimulated Raman scattering(SRS)threshold of highpower fiber amplifiers is demonstrated numerically through a spectral evolution approach.The simulation results confirm that ASE noise in the Raman wavelength band could reduce the SRS threshold of high-power fiber amplifiers significantly.As for ASE noise originated the main amplifier,it becomes stronger and reduces the SRS threshold at shorter operation wavelength below 1052 nm.As for ASE noise originated from the seed laser,it reduces the SRS threshold at different operation wavelength under the condition that the Raman ratio is over-90 dB in the seed laser.The theoretical method and results in this work could provide a well reference to extend the operation wavelength of high-power fiber lasers.

High-power mode-programmable orbital angular momentum beam emitter with an internally sensed optical phased array

The high-power mode-programmable orbital angular momentum(OAM)beam has attracted significant attention in a wide range of applications,such as long-distance optical communication,nonlinear frequency conversion,and beam shaping.Coherent beam combining(CBC)of an optical phased array(OPA)can offer a promising solution for both generating the high-power OAM beam and rapidly switching the OAM modes.However,achieving real-time phase noise locking and formation of desired phase structures in a high-power CBC system faces significant challenges.Here,an internal phase-sensing technique was utilized to generate the high-power OAM beam,which effectively mitigated thermal effects and eliminated the need for large optical devices.An OPA with six elements was employed for experimental demonstration.The first effective generation of over 1.5 kW mode-programmable OAM beam in a continuous-wave domain was presented.Moreover,the results demonstrated that the generated OAM beam could be modulated with multiple dimensions.The topological charge can be switched in real time from-1 to-2.Notably,this OAM beam emitter could function as an OAM beam copier by easily transforming a single OAM beam into an OAM beam array.More importantly,a comprehensive analysis was conducted on power scaling,mode switching speed,and expansion of OAM modes.Additionally,the system’s compact design enabled it to function as a packageable OAM beam emitter.Owing to the advantages of having high power and programmable modes with multiple dimension modulation in phase structures and intensity distribution,this work can pave the way for producing high-power structured light beams and advancing their applications.

近44年藏东南低纬山地降水和气温的气候变化分析

选取1971~2014年藏东南4个气象站逐日气象资料,采用线性趋势、Mann-Kendall非参数检验等方法,分析了藏东南年、季降水量和气温的年际和年代际变化、气候突变。结果表明:近44 a年降水量呈现为减少趋势,平均每10 a减少1.24 mm,春季降水呈增加趋势,其他季节趋于减少,以秋季减少最为明显。年平均气温以0.28℃/10 a的速率显著升高,最高气温和最低气温都出现了升高的趋势。在10 a年际变化尺度上,年平均气温表现为逐年代升高趋势;年降水量在20世纪90年代偏多,其他3个年代均偏少。在时间突变点上,年平均气温出现在1994年;年、季降水量未出现突变。

Helium-hydrogen synergistic effects on swelling in in-situ multiple-ion beams irradiated steels

The development of reliable fusion energy is one of the most important challenges in this century.The accelerated degradation of structural materials in fusion reactors caused by neutron irradiation would cause severe problems.Due to the lack of suitable fusion neutron testing facilities,we have to rely on ion irradiation experiments to test candidate materials in fusion reactors.Moreover,fusion neutron irradiation effects are accompanied by the simultaneous transmutation production of helium and hydrogen.One important method to study the He-H synergistic effects in materials is multiple simultaneous ion beams(MSIB)irradiation that has been studied for decades.To date,there is no convincing conclusion on these He-H synergistic effects among these experiments.Recently,a multiple ion beam in-situ transmission electron microscopy(TEM)analysis facility was developed in Xiamen University(XIAMEN facility),which is the first triple beam system and the only in-running in-situ irradiation facility with TEM in China.In this work,we conducted the first high-temperature triple simultaneous ion beams irradiation experiment with TEM observation using the XIAMEN facility.The responses to in-situ triple-ion beams irradiation in austenitic steel 304L SS and ferritic/martensitic steel CLF-1 were studied and compared with the results in dual-and single-ion beam(s)irradiated steels.Synergistic effects were observed in MSIB irradiated steels.Helium was found to be critical for cavity formation,while hydrogen has strong synergistic effect on increasing swelling.

东亚深部板片水平俯冲和撕裂

从地震层析成像资料推断的地幔中俯冲板片的现今结构是地质时期板块构造运动的结果。位于东亚下方660 lcm地幔不连续面之上的近水平状巨大板片可能是太平洋板块俯冲的残留部分。尽管己有大量的数值模型被用来探索俯冲板片停滞的动力学机制和地球物理参数,但由于板块构造历史的不确定性和地幔的不均一性,人们对这种水平结构板片的演化还没有完全了解。在这里我们提出,在最新的板块构造重建模式限定下的正向地幔流模型基本上可以解释东亚下方地震层析成像中的主要特征。另外,随着菲律宾海板块在中新世期间发生顺时针旋转,强烈的撕裂作用通过俯冲的西太平洋板片传播,导致内部板片的分裂。我们认为,这种与菲律宾海板块旋转有关的撕裂作用也会影响俯冲板片的水平结构。

High-power all-fiber linearly polarized Yb-doped chirped pulse amplifier based on active polarization control

High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demonstrated.The active polarization control technology based on the root-mean-square propagation(RMS-prop)algorithm is employed to guarantee a linearly polarized output from the system.A maximum output power of 402.3 W at a repetition rate of 80 MHz is realized with a polarization extinction ratio(PER)of>11.4 dB.In addition,the reliable operation of the system is verified by examining the stability and noise properties of the amplified laser.The M2factor of the laser beam at the highest output power is measured to be less than 1.15,indicating a diffraction-limited beam quality.Finally,the amplified laser pulse is temporally compressed to 755 fs with a highest average power of 273.8 W.This is the first time,to the best of our knowledge,that the active polarization control technology was introduced into the high-power ultrafast fiber amplifier.

Myeloid-specific targeting of Notch ameliorates murine renal fibrosis via reduced infiltration and activation of bone marrowderived macrophage

Macrophages play critical roles in renal fibrosis.However,macrophages exhibit ontogenic and functional heterogeneities,and which population of macrophages contributes to renal fibrosis and the underlying mechanisms remain unclear.In this study,we genetically targeted Notch signaling by disrupting the transcription factor recombination signal binding protein-JK(RBP-J),to reveal its role in regulation of macrophages during the unilateral ureteral obstruction(UUO)-induced murine renal fibrosis.Myeloid-specific disruption of RBP-J attenuated renal fibrosis with reduced extracellular matrix deposition and myofibroblast activation,as well as attenuated epithelial-mesenchymal transition,likely owing to the reduced expression of TGF-β.Mean while,RBP-J deletion significantly hampered macrophage infiltration and activation in fibrotic kidney,although their proliferation appeared unaltered.By using macrophage clearance experiment,we found that kidney resident macrophages made negligible contribution,but bone marrow(BM)-derived macrophages played a major role in renal fibrogenesis.Further mechanistic analyses showed that Notch blockade reduced monocyte emigration from BM by down-regulating CCR2 expression.Finally,we found that myeloid-specific Notch activation aggravated renal fibrosis,which was mediated by CCR2^+macrophages infiltration.In summary,our data have unveiled that myeloid-specific targeting of Notch could ameliorate renal fibrosis by regulating BM-derived macrophages recruitment and activation,providing a novel strategy for intervention of this disease.

High power all-fiberized and narrow-bandwidth MOPA system by tandem pumping strategy for thermally induced mode instability suppression

An all-fiberized and narrow-bandwidth master oscillator power amplification(MOPA) system with record output power of 4 kW level and slope efficiency of 78% is demonstrated. Tandem pumping strategy is tentatively introduced into the narrow-bandwidth MOPA system for thermally induced mode instability(TMI) suppression. The stimulated Brillouin scattering(SBS) effect is balanced by simply using one-stage phase modulation technique. With different phase modulation signals, SBS limited output powers of 336 W, 1.2 kW and 3.94 kW are respectively achieved with spectral bandwidths accounting for 90% power of ～0.025, 0.17 and ～0.89 nm. Compared with our previous 976 nm pumping system, TMI threshold is overall boosted to be >5 times in which tandem pumping increases the TMI threshold of >3times. The beam quality(M～2 factor) of the output laser is well within 1.5 below the TMI threshold while it is ultimately saturated to be 1.86 with the influence of TMI at maximal output power. Except for SBS and TMI, stimulated Raman scattering(SRS) effect will be another challenge for further power scaling. In such a high power MOPA system, multidetrimental effects(SBS, SRS and TMI) will coexist and may be mutual-coupled, which could provide a well platform for further comprehensively investigating and optimizing the high power, narrow-bandwidth fiber amplifiers.

1.3 kW monolithic linearly polarized single-mode master oscillator power amplifier and strategies for mitigating mode instabilities

We report on the high-power amplification of a 1064 nm linearly polarized laser in an all-fiber polarizationmaintained master oscillator power amplifier,which can operate at an output power level of 1.3 kW.The beam quality(M^2) was measured to be <1.2 at full power operation.The polarization extinction rate of the fiber amplifier was measured to be above 94% before mode instabilities(MIs) set in,which reduced to about 90% after the onset of MI.The power scaling capability of strategies for suppressing MI is analyzed based on a semianalytical model,the theoretical results of which agree with the experimental results.It shows that mitigating MI by coiling the gain fiber is an effective and practical method in standard double-cladding large mode area fiber,and,by tight coiling of the gain fiber to the radius of 5.5 cm,the MI threshold can be increased to three times higher than that without coiling or loose coiling.Experimental studies have been carried out to verify the idea,which has proved that MI was suppressed successfully in the amplifier by proper coiling.

Deep-learning-assisted, two-stage phase control method for high-power mode-programmable orbital angular momentum beam generation

High-power mode-programmable orbital angular momentum(OAM)beams have received substantial attention in recent years.They are widely used in optical communication,nonlinear frequency conversion,and laser processing.To overcome the power limitation of a single beam,coherent beam combining(CBC)of laser arrays is used.However,in specific CBC systems used to generate structured light with a complex wavefront,eliminating phase noise and realizing flexible phase modulation proved to be difficult challenges.In this paper,we propose and demonstrate a two-stage phase control method that can generate OAM beams with different topological charges from a CBC system.During the phase control process,the phase errors are preliminarily compensated by a deep-learning(DL)network,and further eliminated by an optimization algorithm.Moreover,by modulating the expected relative phase vector and cost function,all-electronic flexible programmable switching of the OAM mode is realized.Results indicate that the proposed method combines the characteristics of DL for undesired convergent phase avoidance and the advantages of the optimization algorithm for accuracy improvement,thereby ensuring the high mode purity of the generated OAM beams.This work could provide a valuable reference for future implementation of high-power,fast switchable structured light generation and manipulation.

Clay mineral assemblages of the oceanic red beds in the northern South China Sea and their responses to the Middle Miocene Climate Transition

The Middle Miocene Climate Transition(MMCT,~14 Ma)is the largest cooling event in the Cenozoic“Coolhouse”,which significantly impacts the global chemical weathering pattern.In this paper,the responses of the MMCT global cooling event in the deep South China Sea were studied by clay mineral assemblages analysis of the oceanic red beds(ORB)at International Ocean Discovery Program(IODP)Expedition 368 Site U1502.The results show that the clay mineral assemblages of the ORB at Site U1502 are mainly composed of smectite(56–88%),illite(7–29%),and kaolinite(6–20%),without chlorite.The contents of these clay minerals and illite crystallinity show a four-stage variation pattern during early-middle Miocene(22.8–10.8 Ma).Smectite decreased from average 81%during 22.8–16.2 Ma and 16.2–14.4 Ma to average 67%during 13.8–10.8 Ma,with a rapid decrease of~14%during 14.4–13.8 Ma.On the contrary,illite and kaolinite increased rapidly by~8%and~6%,respectively,during 14.4–13.8 Ma.Illite crystallinity increased from average 0.18°Δ2θduring 22.8–16.2 Ma to average 0.19°Δ2θduring 16.2–14.4 Ma,and then decreased rapidly by~0.02°Δ2θduring 14.4–13.8 Ma.The provenance analysis of clay minerals shows that illite and kaolinite mainly originated from South China landmass due to physical erosion,while smectite mainly came from the Luzon arc as the product of chemical weathering.Therefore,smectite/illite ratio and illite crystallinity are used as proxies of chemical weathering intensity in the early-middle Miocene.High values of the ratio and the crystallinity represent the enhanced chemical weathering,whereas low values indicate the weakened chemical weathering or the strengthened physical erosion process.The smectite/illite ratio and illite crystallinity both decreased rapidly during 14.4–13.8 Ma,indicating the chemical weathering in the surrounding area of the South China Sea weakened rapidly,which we believe is the result of the MMCT event forcing.In addition,their values increased slightly during 16.2–14.4 Ma,which is in response to the relatively enhanced chemical weathering during the Middle Miocene Climate Optimum(MMCO).The variation pattern of clay mineral assemblages of the early-middle Miocene ORB in the South China Sea and its rapid transformation during the MMCT reveal that the Cenozoic cooling played a specific role in controlling the chemical weathering of the Earth’s surface.

Coherent combining of a fiber laser array via cascaded internal phase control technique

We experimentally demonstrated a cascaded internal phase control technique.A laser array with 12 channels was divided into three sub-arrays and a stage array,and phases of the sub-arrays and the stage array were locked by four phase controllers based on the stochastic parallel gradient descent(SPGD)algorithm,respectively.In this way,the phases of the whole array were locked,and the visibility of the interference pattern of the whole emitted laser array in the far field was∼93%.In addition,the technique has the advantage of element expanding and can be further used in the high-power coherent beam combination(CBC)system due to its compact spatial structure.

High-power single-frequency fiber amplifiers:progress and challenge[Invited]

Unlike conventional continuous-wave lasers with wide spectra,the amplification of single-frequency lasers in optical fibers is much more difficult owing to the ultra-high power spectral density induced nonlinear stimulated Brillouin scattering effect.Nevertheless,over the past two decades much effort has been devoted to improving the power scaling and performance of high-power single-frequency fiber amplifiers.These amplifiers are mostly driven by applications,such as high precision detection and metrology,and have benefited from the long coherence length,low noise,and excellent beam quality of this type of laser source.In this paper,we review the overall development of high-power single-frequency fiber amplifiers by focusing on its progress and challenges,specifically,the strategies for circumventing the stimulated Brillouin scattering and transverse mode instability effects that,at present,are the major limiting factors of the power scaling of the single-frequency fiber amplifiers.These factors are also thoroughly discussed in terms of free-space and all-fiber coupled architecture.In addition,we also examine the noise properties of single-frequency fiber amplifiers,along with corresponding noise reducing schemes.Finally,we briefly envision the future development of high-power single-frequency fiber amplifiers.

基于国产卫星遥感的北京冬奥会空气质量监测和追因

2021年9月,高光谱观测卫星高分五号02星成功发射,有效提升了我国大气环境遥感监测的综合应用水平,为空气质量保障提供了自主可控的遥感数据支撑.在2022年1~3月北京-张家口冬奥会期间,我们近实时反演获取了高分五号02星污染气体监测产品,并通过生态环境部卫星环境应用中心为冬奥会提供监测分析日报.本文分析了冬奥会期间北京及周边重点城市的对流层二氧化氮(NO_(2))时空分布特征,探讨了气象条件和人为排放控制措施对冬奥会期间NO_(2)浓度的影响.国产卫星反演结果表明,冬奥会期间华北地区平均对流层NO_(2)柱浓度稳定在3.75×10^(15)molecules/cm^(2)以下,低于会前和会后.不同城市在冬奥会期间NO_(2)柱浓度下降幅度在53.1%~70.1%之间,说明临时管控政策对空气质量改善效果显著,但不同城市的减排实施有差异.这与国控站点近地面NO_(2)监测结果具有较好的一致性.冬奥会期间出现两天NO_(2)浓度高值,主要受不利风场条件影响.本文还通过建立广义相加模型来区分和量化人为减排等非气象因素与气象因素对于对流层NO_(2)浓度变化的贡献,保定、北京、天津和太原在冬奥会期间的NO_(2)浓度分别下降了48.2%、67.5%、48.8%和72.8%,其中人为排放和气象因素分别贡献了41.8%、32.0%、30.0%、42.8%和6.4%、35.6%、18.8%、30.1%.总体上,气象因素影响要弱于排放临时管控措施.该研究首次利用国产卫星为冬奥会提供污染气体监测和溯源分析,有力支撑了我国大气环境遥感监测的应用.

新冠疫情下的股市波动与上市公司应对——基于信号传递视角

新冠疫情给经济社会带来冲击,导致股票市场急剧下跌。在此背景下,基于信号传递的视角,分析上市公司的主动应对策略。研究发现,在疫情爆发的窗口期,上市公司可以通过捐赠公告、业绩提升公告与股票回购公告向市场传递社会责任、经营抗压与股价低估等正向信号。相比对照组,传递正向信号的公司能够获取2%左右的三日累计超额收益。疫情期间的业绩提升信号较非疫情期间有更积极的市场反应,说明投资者存在"秩序需求",在不确定环境中更期待好消息。此外,股票回购作为股价低估的信号工具,能够很好地维护资本市场形象,建议上市公司将股票回购作为稳定股价的"常规武器"以应对资本市场系统性风险。研究为疫情下的企业危机管理提供思路,有助于将灾难转化为财富,提高经济韧性。

First experimental demonstration of coherent beam combining of more than 100 beams

Coherent beam combining of 107 beams has been demonstrated for the first time to the best of our knowledge.When the system was in closed loop,the pattern in far-field was stable and the fringe contrast was>96%.The impact of the dynamic tilt error,the piston error,and power inconsistency was theoretically analyzed.Meanwhile,the distribution law of dynamic tilt error was estimated and the correlation of the tilt dithering of different axis was analyzed statistically.The ratio of power in the central lobe was^22.5%.The phase residue error in the closed loop was~λ∕22,which was evaluated by the root-mean-square error of the signal generated from the photoelectric detector.

Near-diffraction-limited linearly polarized narrow-linewidth random fiber laser with record kilowatt output

In this paper, we propose and experimentally investigate a linearly polarized narrow-linewidth random fiber laser(RFL) operating at 1080 nm and boost the output power to kilowatt level with near-diffraction-limited beam quality using a master oscillation power amplifier. The RFL based on a half-opened cavity, which is composed of a linearly polarized narrow-linewidth fiber Bragg grating and a 500 m piece of polarization-maintained Ge-doped fiber, generates a 0.71 W seed laser with an 88 pm full width at half-maximum(FWHM) linewidth and a 22.5 dB polarization extinction ratio(PER) for power scaling. A two-stage fiber amplifier enhances the seed laser to the maximal 1.01 k W with a PER value of 17 dB and a beam quality of M_x^2=1.15 and M_y^2=1.13. No stimulated Brillouin scattering effect is observed at the ultimate power level, and the FWHM linewidth of the amplified random laser broadens linearly as a function of the output power with a coefficient of about 0.1237 pm∕W.To the best of our knowledge, this is the first demonstration of a linearly polarized narrow-linewidth RFL with even kilowatt-level near-diffraction-limited output, and further performance scaling is ongoing.

All-fiberized and narrow-linewidth 5 kW power-level fiber amplifier based on a bidirectional pumping configuration

In this paper,an all-fiberized and narrow-linewidth 5 kW power-level fiber amplifier is presented.The laser is achieved based on the master oscillator power amplification configuration,in which the phase-modulated single-frequency laser is applied as the seed laser and a bidirectional pumping configuration is applied in the power amplifier.The stimulated Brillouin scattering,stimulated Raman scattering,and transverse mode instability effects are all effectively suppressed in the experiment.Consequently,the output power is scaled up to 4.92 kW with a slope efficiency of as high as approximately 80%.The 3-dB spectral width is about 0.59 nm,and the beam quality is measured to be M^(2)~1.22 at maximum output power.Furthermore,we have also conducted a detailed spectral analysis on the spectral width of the signal laser,which reveals that the spectral wing broadening phenomenon could lead to the obvious decrease of the spectral purity at certain output power.Overall,this work could provide a reference for obtaining and optimizing high-power narrow-linewidth fiber lasers.

Deep-learning-based phase control method for tiled aperture coherent beam combining systems

We incorporate deep learning(DL)into tiled aperture coherent beam combining(CBC)systems for the first time,to the best of our knowledge.By using a well-trained convolutional neural network DL model,which has been constructed at a non-focal-plane to avoid the data collision problem,the relative phase of each beamlet could be accurately estimated,and then the phase error in the CBC system could be compensated directly by a servo phase control system.The feasibility and extensibility of the phase control method have been demonstrated by simulating the coherent combining of different hexagonal arrays.This DL-based phase control method offers a new way of eliminating dynamic phase noise in tiled aperture CBC systems,and it could provide a valuable reference on alleviating the long-standing problem that the phase control bandwidth decreases as the number of array elements increases.